‰  NOW 35 WPM  ‰

C201 AND C210 PROVIDE COMPENSATION FOR THE CAPACITANCE OF THE CAT5 CABLE ON
THE OP AMP INPUT.  U202 IS A RAIL SPLITTER TO ESTABLISH LOCAL DC GROUND.
THIS RAIL SPLITTER MUST SUPPLY THE DC COMPONENT OF THE OUTPUT SIGNAL FROM
U201.  THE DC SUPPLY VOLTAGE CAN BE ANYTHING FROM ABOUT 0 TO 24 V.  SUPPLY
CURRENT FOR BOTH THE PREAMP AND THE SUMMING AMP TOGETHER IS ABOUT 35 MA.  A
HIGHER SUPPLY VOLTAGE WILL ALLOW THE OP AMP OUTPUTS TO SWING FURTHER
WITHOUT SATURATING ON STRONG LOCAL SIGNALS, BUT IN NO CASE SHOULD THE OP
AMP MAXIMUM RATING OF 24 V BE EXCEEDED.  A SPLIT SUPPLY R5 V TO R12 V CAN
ALSO BE USED, IN WHICH CASE THE RAIL SPLITTER OP AMP CAN BE OMITTED.
CONSTRUCTION  SMALL PRINTED CIRCUIT BOARDS PC BOARDS WERE FABRICATED FOR
THE CIRCUITS AS SHOWN IN FIGURE 4.  OTHERS SHOULD BE ABLE TO MAKE THEIR OWN
BOARDS USING ONE OF THE PROTOTYPING SERVICES SUCH AS EXPRESSPCB.  THE
CIRCUITS CAN ALSO BE BUILT DEAD BUG STYLE ON SMALL PIECES OF COPPER CLAD
BOARD.  THE PREAMP CIRCUIT IS HOUSED IN A 3 4 INCH PVC ELECTRICAL T, SHOWN
IN FIGURE 5.  THE DIPOLE ELEMENTS ARE 1/16 INCH BRAZING RODS APPROXIMATELY
45 CENTIMETERS LONG, HELD IN PLACE BY 1/2 INCH PVC PLUGS THREADED INTO
BUSHINGS THAT ARE GLUED INTO THE ENDS OF THE PVC T.  INSIDE THE T, THE ENDS
OF THE BRAZING RODS ARE CONNECTED TO THE PC BOARD BY SHORT LENGTHS OF THIN
WIRE.  THE HOLES THROUGH THE PVC PLUGS FOR THE DIPOLE ELEMENTS ARE SEALED
‰  END OF 35 WPM TEXT  ‰  QST DE W1AW  ƒ